A Fire and Emergency New Zealand (Fenz) spokeswoman said crews from four fire stations attended the property in Rockside Rd, Woodhaugh, shortly before 9am yesterday.
Willowbank Station Officer Pete O'Shea said the fire started on the ground floor and moved to the roof.
There were no smoke alarms in the house and he wanted to stress to the public their importance.
The occupants of the house had left to take their children to school and returned to find the blaze.
The home was extensively damaged, particularly in the kitchen area.
A St John spokesman said an ambulance attended the fire and assessed one patient for smoke inhalation, but he declined treatment.
Smoke could be seen billowing from the house around 9am, and firefighters had to smash glass panes in the front door and drag furniture out of the property in order to get a fire hose in.
A duty fire investigator was on his way to look at the cause of the fire, he said.
The fire extinguished by about 10.30am.
